The present invention relates to a physical quantity detection apparatus, a method of controlling a physical quantity detection apparatus, an abnormality diagnosis system, an abnormality diagnosis method, etc.
A physical quantity detection apparatus that detects a physical quantity has been known. For example, an angular velocity detection apparatus that detects an angular velocity as the physical quantity has been known. An electronic instrument or a system that includes an angular velocity detection apparatus and performs a control process based on the angular velocity detected by the angular velocity detection apparatus has been widely used. For example, a vehicle travel control system prevents a side skid based on the angular velocity detected by the angular velocity detection apparatus.
Such an electronic instrument or system performs wrong control if the angular velocity detection apparatus breaks down. Therefore, measures such as lighting an alarm lamp when the angular velocity detection apparatus has broken down have been employed. Various technologies that diagnose failure of the angular velocity detection apparatus have been proposed. For example, Japanese Patent No. 3520821 discloses a vibrating gyro apparatus that includes a self-diagnosis circuit that superimposes an offset signal on at least one signal output from a detection means of a vibrator to detect an open circuit or a short circuit of the detection means. JP-A-2001-304871 discloses an angular velocity sensor abnormality diagnosis apparatus that performs abnormality diagnosis during a primary check based on the level of the angular velocity output signal in a state in which an inspection signal (e.g., pseudo-rotation signal) is input to a sensor element.
The vibrating gyroscope apparatus disclosed in Japanese Patent No. 3520821 is configured so that the offset signal is generated in the preceding stage of a differential amplifier means, and an abnormality of the detection means is detected based on a signal component due to the offset signal. This method can detect a circuit abnormality in the subsequent stage of the differential amplifier means, but cannot detect an element abnormality or a circuit abnormality in the preceding stage of the differential amplifier means.
Since the abnormality diagnosis apparatus disclosed in JP-A-2001-304871 performs abnormality diagnosis based on the level of the angular velocity output signal in a state in which the inspection signal (e.g., pseudo-rotation signal) is input to the sensor element, it may be possible to detect an element abnormality. However, since the abnormality diagnosis apparatus disclosed in JP-A-2001-304871 inputs the inspection signal (e.g., pseudo-rotation signal) that is not present during a normal angular velocity detection operation to the sensor element, an element abnormality that occurs during a normal angular velocity detection operation cannot be accurately detected. This poses a reliability problem.